Contribution to the modelling of refrigeration systems

The main objective of this study is to propose and to validate simplified models to simulate the performance of refrigeration systems.The proposed modelling approach of the system is modular: the compressor is modelled by a simple and physical model that takes into account the heat transfers and the un-matching of internal and external pressure ratio for the scroll compressors. The evaporator is modelled as a two zones heat exchanger on the refrigeration side (one for the two phases zone and the other one for superheated gas) and finally the condenser is assumed to be divided into three zones (de-superheating, two-phase and the sub-cooling).The compressor model was already developed by other author; here it is only validated using three scroll compressors and two reciprocating ones. The main differences are the conditions at which these compressors are tested: 20 bar at the supply and 40 at the exhaust.The condenser and evaporator models are the main contribution of this study. These models use the geometry and the correlation from the literature to calculate the global heat transfer coefficient on each zone. In the case of the condenser, a mean void fraction model is used to determinate the condenser subcooling as function of the refrigerant charge or vice-versa.The refrigeration system model is validated with experimental results obtained on each component and the whole system in five different test benches. The results show a very good agreement between the measured and predicted main outputs of the system.